The fastening of fibre composite components, eg polymer components of fibre glass or carbon fibres, which are subjected to loads from other structural elements, is often troublesome. One of these problems occurs when a wind turbine blades is to be secured to the hub of the wind turbine in such a manner that the connection therebetween is able to transfer heavy dynamic forces. The end face of a rotor blade root is often circular and secured to a circular metal flange on the turbine hub by means of bolts or threaded rods.
U.S. Pat. No. 4,915,590 discloses several methods for attaching the root of a wind turbine blade to a flange on the hub. The publication thus discloses a method, whereby the blade wall in the root is provided with embedded, elongated embedding elements in form of sucker rods comprising a fibre glass rod, one end of the rod being provided with a coupling in form of a female-treaded steel bushing. The embedding elements are embedded such in the blade wall at the root that the female thread of the steel bushings is accessible from the end face of the blade root for attachment thereof to the hub.
One drawback of this method is that it is time-consuming to position the embedding elements accurately in the mould and subsequently thereto place fibre mats in abutment with the element to ensure a durable embedment. Due to the circular shape of the rods, the fibre mats have to be pushed downwards on either side, and even if this is achieved, folds are created in the fibres/fibre mats which weaken the strength and which in turn cause a risk of delamination due to the heavy dynamic loads.